Task 1: Write a program using both external interrupt and PORTB interrupt to adjust a PWM signal.

• Connections: Two buttons at RB0 and RB4. One LED at RA1

• Concept: There are two delay loops named t_up and t_down. Their total is always constant T.

• Main program: Star with t_up = t_down. In an infinite loop, turn on the LED and wait for t_up, turn off LED and wait for t_down.

• External Interrupt: Increase t_up by 10% of T. If t_up is 100% of T don’t increase.

• PORTB Interrupt: Decrease t_up by 10% of T. If t_up is 0% of T don’t decrease.

Write button functions.